Petroleum refining and petrochemical processes frequently involve treating processes for removing sulfur compounds from hydrocarbon streams. In these processes, mercaptans present in a liquid hydrocarbon stream such as naphtha or LPG are extracted into an aqueous alkaline solution. The extracted mercaptans may be oxidized to disulfide compounds.
The sweetening process requires an oxygen supply stream, typically air, to supply the required oxygen. An admixture of hydrocarbon and an oxidation catalyst in an aqueous alkaline environment can be passed to an oxidation vessel to be contacted with air. The oxidation catalyst may be impregnated on a solid composite or may be dispersed or dissolved in the aqueous alkaline solution. A commonly employed oxidation catalyst comprises a metal phthalocyanine compound, which may be dissolved in an alkaline solution or may be impregnated on activated charcoal. Suitable catalysts are described in U.S. Pat. Nos. 2,853,432; 4,049,572 and 4,923,596.
The reaction rate (activity) of the catalyst in the extractive processes is an important factor for efficient removal of mercaptans from hydrocarbon streams. If higher catalyst activity could be achieved then less catalyst could be used or greater amounts of hydrocarbon could be processed, ultimately resulting in economic advantages or improved process efficiency.
Accordingly, there is a constant desire for improved catalysts for converting mercaptans to disulfides.